PlanCache.list()
Definition
PlanCache.list(<pipeline>)
Returns an array of plan cache entries for a collection.
The method is only available from the
plan cache object
of a specific collection; i.e.db.collection.getPlanCache().list(<pipeline>) ParameterTypeDescriptionArrayOptional. Aggregation pipeline to filter/process the plan cache query shapes.
You can run this method from a
mongod
ormongos
instance. When run on a sharded cluster, the method returns plan cache entry information from a single member in each shard replica set. This member is identified with the shard and host fields. See also Read Preference.The method
PlanCache.list()
wraps the$planCacheStats
aggregation pipeline. That is,db.collection.getPlanCache().list([<stage1>, <stage2>, ...] ) is equivalent to
db.collection.aggregate([ <$planCacheStats stage>, <stage1>, <stage2>, ... ]).toArray(); For details on the output, see $planCacheStats output.
Not all queries automatically place a query plan in the cache.
PlanCache.list()
returns an empty array if there are currently no plan cache query shapes with cached query plans.
Compatibility
This method is available in deployments hosted in the following environments:
MongoDB Atlas: The fully managed service for MongoDB deployments in the cloud
MongoDB Enterprise: The subscription-based, self-managed version of MongoDB
MongoDB Community: The source-available, free-to-use, and self-managed version of MongoDB
Considerations
Query Settings
Starting in MongoDB 8.0, use query settings instead of adding index filters. Index filters are deprecated starting in MongoDB 8.0.
Query settings have more functionality than index filters. Also, index
filters aren't persistent and you cannot easily create index filters for
all cluster nodes. To add query settings and explore examples, see
setQuerySettings
.
Restrictions
PlanCache.list()
is not allowed in transactions.
Query Hash and Plan Cache Query Shapes
To help identify slow queries with the same plan cache query shape, each plan cache query shape is associated with a query hash. The plan cache query shape hash is a hexadecimal string that represents a hash of the query shape and is dependent only on the query shape.
Note
As with any hash function, two different query shapes may result in the same hash value. However, the occurrence of hash collisions between different query shapes is unlikely.
Starting in MongoDB 8.0, the pre-existing queryHash
field is renamed
to planCacheShapeHash
. If you're using an earlier MongoDB version,
you'll see queryHash
instead of planCacheShapeHash
.
The query optimizer only caches the plan for a plan cache query shape that can have more than one viable plan.
Each entry in the plan cache is associated with a planCacheShapeHash
.
Warning
Starting in MongoDB 8.0, the pre-existing queryHash
field is renamed
to planCacheShapeHash
. If you're using an earlier MongoDB version,
you'll see queryHash
instead of planCacheShapeHash
.
Read Preference
PlanCache.list()
observes the read preference in selecting the host(s) from which to return
the plan cache information.
Applications may target different members of a replica set. As such,
each replica set member might receive different read commands and have
plan cache information that differs from other members. Nevertheless,
running PlanCache.list()
on a replica set or a sharded
cluster obeys the normal read preference rules. That is, on a replica
set, the operation gathers plan cache information from just one member
of replica set, and on a sharded cluster, the operation gathers plan
cache information from just one member of each shard replica set.
Required Access
On systems running with authorization
, the user
must have the planCacheRead
privilege for the collection.
Examples
Note
Not all queries automatically place a query plan in the cache.
PlanCache.list()
returns an empty array if there are currently no query shapes with cached query plans.For details on the output, see $planCacheStats output.
The examples in this section use the following orders
collection:
db.orders.insertMany( [ { "_id" : 1, "item" : "abc", "price" : NumberDecimal("12"), "quantity" : 2, "type": "apparel" }, { "_id" : 2, "item" : "jkl", "price" : NumberDecimal("20"), "quantity" : 1, "type": "electronics" }, { "_id" : 3, "item" : "abc", "price" : NumberDecimal("10"), "quantity" : 5, "type": "apparel" }, { "_id" : 4, "item" : "abc", "price" : NumberDecimal("8"), "quantity" : 10, "type": "apparel" }, { "_id" : 5, "item" : "jkl", "price" : NumberDecimal("15"), "quantity" : 15, "type": "electronics" } ] )
Create the following indexes on the collection:
db.orders.createIndex( { item: 1 } ); db.orders.createIndex( { item: 1, quantity: 1 } ); db.orders.createIndex( { item: 1, price: 1 }, { partialFilterExpression: { price: { $gte: NumberDecimal("10")} } } ); db.orders.createIndex( { quantity: 1 } ); db.orders.createIndex( { quantity: 1, type: 1 } );
Note
Index { item: 1, price: 1 }
is a partial index and only indexes documents with price
field greater than or equal to NumberDecimal("10")
.
Run some queries against the collection:
db.orders.find( { item: "abc", price: { $gte: NumberDecimal("10") } } ) db.orders.find( { item: "abc", price: { $gte: NumberDecimal("5") } } ) db.orders.find( { quantity: { $gte: 20 } } ) db.orders.find( { quantity: { $gte: 5 }, type: "apparel" } )
Return Information for All Entries in the Query Cache
The following returns the plan cache query shapes that have
cached plans for the orders
collection:
db.orders.getPlanCache().list()
The method returns an array of the plan cache query shapes currently in the cache.
In the example, the orders
collection had cached query plans
associated with the following shapes:
[ { "createdFromQuery" : { "query" : { "quantity" : { "$gte" : 5 }, "type" : "apparel" }, "sort" : { }, "projection" : { } }, "planCacheShapeHash" : "4D151C4C", "planCacheKey" : "DD67E353", "isActive" : false, "works" : NumberLong(4), "cachedPlan" : { "stage" : "FETCH", "filter" : { "type" : { "$eq" : "apparel" } }, "inputStage" : { "stage" : "IXSCAN", "keyPattern" : { "quantity" : 1 }, "indexName" : "quantity_1", "isMultiKey" : false, "multiKeyPaths" : { "quantity" : [ ] }, "isUnique" : false, "isSparse" : false, "isPartial" : false, "indexVersion" : 2, "direction" : "forward", "indexBounds" : { "quantity" : [ "[5.0, inf.0]" ] } } }, "timeOfCreation" : ISODate("2020-02-06T15:57:18.219Z"), "creationExecStats" : [ { "nReturned" : 2, "executionTimeMillisEstimate" : 0, "totalKeysExamined" : 3, "totalDocsExamined" : 3, "executionStages" : { "stage" : "FETCH", "filter" : { "type" : { "$eq" : "apparel" } }, "nReturned" : 2, "executionTimeMillisEstimate" : 0, "works" : 4, ... } }, { "nReturned" : 2, "executionTimeMillisEstimate" : 0, "totalKeysExamined" : 3, "totalDocsExamined" : 2, "executionStages" : { "stage" : "FETCH", "nReturned" : 2, "executionTimeMillisEstimate" : 0, "works" : 4, ... } } ], "candidatePlanScores" : [ 1.5002, 1.5002 ], "indexFilterSet" : false, "estimatedSizeBytes" : NumberLong(3160), // Available starting in MongoDB 5.0 "host" : "mongodb1.example.net:27018", "shard" : "shardA" // Available if run on sharded cluster }, { "createdFromQuery" : { "query" : { "quantity" : { "$gte" : 20 } }, "sort" : { }, "projection" : { } }, "planCacheShapeHash" : "23B19B75", "planCacheKey" : "6F23F858", "isActive" : false, "works" : NumberLong(1), ... }, { "createdFromQuery" : { "query" : { "item" : "abc", "price" : { "$gte" : NumberDecimal("5") } }, "sort" : { }, "projection" : { } }, "planCacheShapeHash" : "117A6B10", "planCacheKey" : "A1824628", "isActive" : false, "works" : NumberLong(4), ... }, { "createdFromQuery" : { "query" : { "item" : "abc", "price" : { "$gte" : NumberDecimal("10") } }, "sort" : { }, "projection" : { } }, "planCacheShapeHash" : "117A6B10", "planCacheKey" : "2E6E536B", "isActive" : false, "works" : NumberLong(3), ... } ]
Warning
Starting in MongoDB 8.0, the pre-existing queryHash
field is renamed
to planCacheShapeHash
. If you're using an earlier MongoDB version,
you'll see queryHash
instead of planCacheShapeHash
.
For details on the output, see $planCacheStats output.
List Plan Cache Query Shapes
To obtain a list of all of the query shapes for which there is a cached plan,
you can use the PlanCache.list()
. For example, the following operation
passes in a pipeline with a $project
stage to only output the
createdFromQuery field and the
planCacheShapeHash field.
db.orders.getPlanCache().list( [ { $project: {createdFromQuery: 1, planCacheShapeHash: 1 } } ] )
Warning
Starting in MongoDB 8.0, the pre-existing queryHash
field is renamed
to planCacheShapeHash
. If you're using an earlier MongoDB version,
you'll see queryHash
instead of planCacheShapeHash
.
The operation returns the following plan cache query shapes:
[ { "createdFromQuery" : { "query" : { "quantity" : { "$gte" : 5 }, "type" : "apparel" }, "sort" : { }, "projection" : { } }, "planCacheShapeHash" : "4D151C4C" }, { "createdFromQuery" : { "query" : { "quantity" : { "$gte" : 20 } }, "sort" : { }, "projection" : { } }, "planCacheShapeHash" : "23B19B75" }, { "createdFromQuery" : { "query" : { "item" : "abc", "price" : { "$gte" : NumberDecimal("5") } }, "sort" : { }, "projection" : { } }, "planCacheShapeHash" : "117A6B10" }, { "createdFromQuery" : { "query" : { "item" : "abc", "price" : { "$gte" : NumberDecimal("10") } }, "sort" : { }, "projection" : { } }, "planCacheShapeHash" : "117A6B10" } ]
For details on the output, see $planCacheStats output.
Find Cache Entry Details for a Plan Cache Query Shape
To return plan cache information for a particular query shape, pass in
a pipeline with a $match
on the planCacheKey field.
db.orders.getPlanCache().list([ { $match: { planCacheKey: "DD67E353"} } ] )
The operation returns the following:
[ { "createdFromQuery" : { "query" : { "quantity" : { "$gte" : 5 }, "type" : "apparel" }, "sort" : { }, "projection" : { } }, "planCacheShapeHash" : "4D151C4C", "planCacheKey" : "DD67E353", "isActive" : false, "works" : NumberLong(4), "cachedPlan" : { "stage" : "FETCH", "filter" : { "type" : { "$eq" : "apparel" } }, "inputStage" : { "stage" : "IXSCAN", "keyPattern" : { "quantity" : 1 }, "indexName" : "quantity_1", "isMultiKey" : false, "multiKeyPaths" : { "quantity" : [ ] }, "isUnique" : false, "isSparse" : false, "isPartial" : false, "indexVersion" : 2, "direction" : "forward", "indexBounds" : { "quantity" : [ "[5.0, inf.0]" ] } } }, "timeOfCreation" : ISODate("2020-02-11T17:14:33.873Z"), "creationExecStats" : [ { "nReturned" : 2, "executionTimeMillisEstimate" : 0, "totalKeysExamined" : 3, "totalDocsExamined" : 3, "executionStages" : { "stage" : "FETCH", "filter" : { "type" : { "$eq" : "apparel" } }, "nReturned" : 2, "executionTimeMillisEstimate" : 0, "works" : 4, "advanced" : 2, "needTime" : 1, "needYield" : 0, "saveState" : 0, "restoreState" : 0, "isEOF" : 1, "docsExamined" : 3, "alreadyHasObj" : 0, "inputStage" : { "stage" : "IXSCAN", "nReturned" : 3, "executionTimeMillisEstimate" : 0, "works" : 4, "advanced" : 3, "needTime" : 0, "needYield" : 0, "saveState" : 0, "restoreState" : 0, "isEOF" : 1, "keyPattern" : { "quantity" : 1 }, "indexName" : "quantity_1", "isMultiKey" : false, "multiKeyPaths" : { "quantity" : [ ] }, "isUnique" : false, "isSparse" : false, "isPartial" : false, "indexVersion" : 2, "direction" : "forward", "indexBounds" : { "quantity" : [ "[5.0, inf.0]" ] }, "keysExamined" : 3, "seeks" : 1, "dupsTested" : 0, "dupsDropped" : 0 } } }, { "nReturned" : 2, "executionTimeMillisEstimate" : 0, "totalKeysExamined" : 3, "totalDocsExamined" : 2, "executionStages" : { "stage" : "FETCH", "nReturned" : 2, "executionTimeMillisEstimate" : 0, "works" : 4, "advanced" : 2, "needTime" : 1, "needYield" : 0, "saveState" : 0, "restoreState" : 0, "isEOF" : 1, "docsExamined" : 2, "alreadyHasObj" : 0, "inputStage" : { "stage" : "IXSCAN", "nReturned" : 2, "executionTimeMillisEstimate" : 0, "works" : 4, "advanced" : 2, "needTime" : 1, "needYield" : 0, "saveState" : 0, "restoreState" : 0, "isEOF" : 1, "keyPattern" : { "quantity" : 1, "type" : 1 }, "indexName" : "quantity_1_type_1", "isMultiKey" : false, "multiKeyPaths" : { "quantity" : [ ], "type" : [ ] }, "isUnique" : false, "isSparse" : false, "isPartial" : false, "indexVersion" : 2, "direction" : "forward", "indexBounds" : { "quantity" : [ "[5.0, inf.0]" ], "type" : [ "[\"apparel\", \"apparel\"]" ] }, "keysExamined" : 3, "seeks" : 2, "dupsTested" : 0, "dupsDropped" : 0 } } } ], "candidatePlanScores" : [ 1.5002, 1.5002 ], "indexFilterSet" : false, "estimatedSizeBytes" : NumberLong(3160), // Available starting in MongoDB 5.0 "host" : "mongodb1.example.net:27018", "shard" : "shardA" // Available if run on sharded cluster } ]
Warning
Starting in MongoDB 8.0, the pre-existing queryHash
field is renamed
to planCacheShapeHash
. If you're using an earlier MongoDB version,
you'll see queryHash
instead of planCacheShapeHash
.
For details on the output, see $planCacheStats output.